Two forensic experts have visited a Highland quarry which could hold the key to a 27-year-old mystery.

Professor Sue Black, who investigated war crimes in Kosovo, and Professor John Hunter were asked by police to look at Dalmagarry quarry.

The site is near where Renee MacRae's burnt-out car was discovered in a lay-by on the A9 in 1976. She and her three-year-old son were missing.

A decision to search the quarry for their bodies may be taken soon.

The disappearance of Renee and Andrew MacRae has resulted in one of Scotland's largest missing persons inquiries.

In February, a retired police officer said he believed their bodies may be in the quarry, which is several hundred yards from the lay-by 12 miles south of Inverness.

We are not at the stage of telling them how to conduct any search. It is a very preliminary stage

Professor Sue Black

The officer said he was close to discovering the bodies 20 years ago when he smelled decaying flesh but claimed he was not allowed to continue the investigation.

Professor Black, of Dundee University, who headed the British forensic team in Kosovo for the International War Crimes Tribunal, said she and her colleague had been asked by Northern Constabulary to look at the site.

"It is a substantial area and it will be very complicated to search," she cautioned.

"We are not at the stage of telling them how to conduct any search. It is a very preliminary stage. We are here to look at possibilities."

'Mammoth task'

Professor Hunter, of Birmingham University, said there were many factors to be considered such as the type of deposits and the history of the site.

"We are going to evaluate what could be done here physically as well as look at the technological options available which could provide a shortcut and narrow down a search area," he added.

Detective Superintendent Gordon Urquhart described the prospect of searching the entire quarry as a "mammoth task" which would be costly and would take many weeks.

But he stressed that the force had not "given up" on Renee MacRae and her son.